1. Field of the Invention
The present invention relates to a contactor assembly of a prober apparatus for use in circuit inspection of plural semiconductor chips formed over a semiconductor wafer in the fabrication of an electronic device, such as an LSI, and more particularly to multiple beam-synthesized type contactor assembly used in a prober apparatus for use in a probing test to collectively measure the electrical conduction characteristics of semiconductor chips by bringing vertical probes into contact with circuit terminals (pads) arrayed on semiconductor chips intact in a wafer state.
2. Description of Prior Art
Along with the advancement of semiconductor technology, the scale of integration of electronic devices has become enlarged and the area occupied by circuit wiring in each of the semiconductor chips formed over a semiconductor wafer has become greater, resulting in an increase in the number of circuit terminals (pads) on each semiconductor chip, and this problem is being addressed by miniaturization of pad arrays through contraction of the pad area and of the pad pitch. At the same time, the chip size package (CSP) system in which semiconductor chips are not accommodated in a package and instead mounted bare over a circuit board or the like is becoming the main stream, and this makes it indispensable to check the characteristics and determine the acceptability of the wafer before it is divided into semiconductor chips.
A particular problem ensuing from the miniaturization of pad arrays (narrowed pitch) is that the probe structure for achieving electrical continuity by establishing contact with the pads of semiconductor chips in subjecting an electronic device to electrical characteristics tests or circuit inspection should be matched with the miniaturization of pad arrays, and various measuring devices or methods are used to keep abreast of this increasing miniaturization of pad arrays.
For instance, there is a method to have a contactor assembly, which includes plural acicular probes each having an elastic deformable part which is elastically deformed by an external force, intervene between the pads of semiconductor chips and the testing device. This contactor assembly and the test circuit of semiconductor chips are electrically connected by a printed circuit board known as a probe card.
Generally in a probe card, where acicular probes having a cantilever structure are used, the tips of probes in contact with the pads of semiconductor chips are arrayed in a narrow pitch. However, the root parts in contact with the probe card can be wider in pitch because probes are radially arranged, expanding toward the tips, and enables the probes to be soldered, or otherwise fitted, to the circuit terminals of the probe card. This cantilever structure, however, involves a problem that the probe tips, when coming into contact with pads, deviate in the horizontal direction and therefore damage the pads or go off the pads to invite a drop in measurement yield. Furthermore, only one chip can be measured at a time. The fitting accuracy varies from probe to probe, making it difficult to control the contact pressure to a constant level.
In vertical probes, in which probes are vertically fixed to the circuit terminals of a probe card instead of being cantilevered, the pitch of pads on the semiconductor chips and that of circuit terminals on the probe card have to be equal. However, available manufacturing techniques are not adequate for required miniaturization of the circuit pattern on the probe card, which is a printed circuit board, and it is therefore difficult to meet the requirement to match the area occupied by circuit terminals and the wiring width with the pad pitch. Furthermore, as there is a limit to the pitch that allows soldering, it becomes impossible to keep up with the advancement of miniaturization in fixing the vertical probes vertically to the probe card to match the pad pitch of the semiconductor chips.
Thus, a large proportion of the planar area is occupied by the circuit wiring width in addition to the area of circuit terminals on the probe card, preventing the pitch of circuit terminals from being narrowed. To address this problem, the number of vertical probes is maintained by use of a multi-layered printed circuit board as the probe card, arraying circuit terminals in a grid form or a two-row zigzag pattern and electrically connecting inter-layer wires by through holes. However, as these through holes occupy a large space, the presence of the through holes constitutes a cause of preventing the pitch of circuit terminals from being narrowed. Thus, an attempt to fix vertical probes to the probe card in this way involves the need for sophisticated skills and a large number of man-hours in soldering in addition to the difficulty to narrow the pitch of circuit terminals, resulting in a high cost. In order to solve these problems, the present inventors proposed a vertical contactor assembly, and have also proposed a prober apparatus using this vertical contactor assembly (see Patent Document 1 and Patent Document 2).
The vertical contactor assembly proposed by the present inventors, cited here as an instance of the prior art, includes vertical copper probes each formed by sticking a thin copper sheet onto the surface of a ribbon-shaped (strip-shaped) resin film and etching this copper sheet to create a curved part in the resin film surface as shown in FIG. 22 of Patent Document 2, and the vertical contactor assembly is configured by stacking plural these probe-stuck resin films.
This vertical contactor assembly, since it is structured by stacking resin films, permits arrangement of plural probes in a very limited area and, as each resin film has an aperture and the vertical part of each probe is curved on the way along the edge of the aperture, the distortion due to the pressure when the tips of the probes have come into contact with the pads can be absorbed by the apertures in the resin films and the curved parts of the probes.
Regarding the way to let the pressure work on the probes and resin films during measurement, the inventors have proposed various shapes by designing in different ways the size and shape of the apertures of the resin films and the curved shape of the probes. In particular, they recently proposed probes whose electric conduction pattern is linked with a multiple beam-synthesized type contactor assembly. However, even though a contactor assembly adapted to a narrowed pitch is made available, more complex machining of resin films and probes involves a problem of increased costs.
Patent Document 1: JP-A-338133/2000
Patent Document 2: JP-A-274010/2004
As stated above, the prober apparatus using a film-stacked type vertical contactor assembly proposed by the present inventors is applicable to measurement of semiconductor chips whose pad pitch is as narrow as 45 μm or less (20 μm for instance). Moreover, as it permits automatic assembling of probes without needing fixation by soldering or with resin, such apparatuses can be mass-produced at low cost, and provide an additional major advantage of allowing the contact pressure to be uniformly controlled for every probe because collective vertical contact with chip pads is possible.
However, this earlier proposed contactor assembly configuration involves a problem of increased electrostatic capacitance, which makes it unsuitable for measurement, when it is to be applied to the testing of a device for high frequency use because of the absence of a magnetic shield function.
Moreover, where plural chips having rectangularly arrayed pads are to be tested at the same time, if any overlapping in the z-direction (the vertical direction, the same applies in the rest of this specification) occurs, a parallel spring link mechanism makes the vertical probes taller on account of the narrow spacing between adjoining chips, making the probes susceptible to buckling or deformation.
A first object of the present invention is to provide a contactor assembly which has a simple structure of a small surface area, close to the cantilever structure, for the shape of vertical probes to be formed over resin films, in which a parallel spring structure is formed between electroconductive beams and deformable beams by having the utilization of the deformable beams among cantilevers, whose electrical characteristic in particular is small in electrostatic capacitance and which are unrelated to electrostatic capacitance, and whose vertical probes are given a mechanical characteristic of allowing the overdrive due to parallel operation to be increased.
A second object of the invention is to provide a multiple beam-synthesized type contactor assembly which is made easier to machine, features of which include a reduction in the number of man-hours spent on the formation of apertures in resin films.
A third object of the invention is to provide a contactor assembly which is made usable, in the manufacturing processes of electronic devices such as LSIs, in probing tests to collectively measure the electrical conduction characteristics of semiconductor chips by bringing vertical probes still in a wafer state into contact with circuit terminals (pads) arrayed on multiple chips, and also usable as contactors for checking the lighting of liquid crystals.